Methods for manufacturing fabric-type artificial leathers are known. One such method is described in DE-OS No. 19 17 457. There, a fabric of shrinkable polyvinyl alcohol (PVA) fibers, densified by needling, is subjected to a shrinking process by immersion in hot water and is treated sequentially or simultaneously with a water-soluble synthetic resin and an aqueous PVA solution. The PVA introduced into the fabric by aqueous solution is subsequently coagulated and cross-linked when the fabric is immersed in acidified formalin. Also during immersion in the formalin, the water-soluble synthetic resin is at least partially removed. However, such removal is a time-consuming process. Moreover, this method is undesirable because it is not possible to carry out the method without interruption, and considerable waste water problems arise. Also, the fabric products are characterized by low mechanical strength and are not suited for applications requiring a high-quality application.
Another method is disclosed in DE-OS No. 19 05 551, wherein a flexible sheet material is described which is particularly suited as a raw material for the manufacture of artificial leather. The product obtained comprises a needled and shrunk nonwoven fabric of PVA fibers with a titer of 0.5 to 2.5 den. The voids of the fabric contain an optional grinding powder and a polymer filler which does not adhere to the fibers, but which hangs together largely via the spaces between the fibers. Due to its high moisture absorptivity, this fabric has little dimensional stability. Furthermore, the feel and drapability differ substantially from the corresponding properties of natural leather, so that this fabric makes a poor substitute for natural leather.
DE-OS No. 28 56 091 discloses a needled and thermally welded nonwoven fabric comprised of multi-component fibers of the matrix-segment type, which fibers are split by heat-induced shrinkage into partial fibers with a titer between about 0.1 to 20 dtex. The planar structure of such a fabric has little mechanical strength and exhibits no properties similar to natural leather.
In DE-OS No. 20 34 195, a method for manufacturing an artificial leather is described, in which composite fibers are combined with an embedment and an island component to form a fabric material, the three-dimensional structure of which is densified by needling. The nonwoven fabric obtained in this manner is then impregnated with a water-soluble polymer, whereupon the embedment is subsequently removed from the fabric by treatment with a solvent. The retained island component is thereby released. The fabric material containing the island component is impregnated with an elastic polymer which solidifies. Subsequently the water-soluble polymer is washed out; the nonwoven fabric is cut parallel to the surface into two pieces, and the surface so obtained is roughened with sandpaper in order to obtain a uniform and dense nap. The method suffers from the fact it is complicated and expensive in practical application. Furthermore, the substantial quantities of organic solvents are removed only with difficulty and pose environmental pollution problems.
In summary, it has been found that there are narrow limits to the practical application of the state of the art methods for manufacturing artificial leather fabrics. One concern is the economic feasibility of the known methods since such methods provide very low production from very expensive facilities, which are otherwise not commonly used in nonwoven fabric products. Another practical limitation of the state of the art methods is the products obtained thereby frequently exhibit undesirable characteristics such as poor light fastness, a brittle feel, poor drapability, unsatisfactory "breathing" and low abrasion resistance. As a consequence, the use of these products for certain high-quality ends, such as covering an automobile seat or manufacturing outerwear becomes at the very least problematical.
It is an object of the present invention to provide a method for economically producing a high-quality artificial leather distinguished by a soft drape, good light fastness, good breathing and good abrasion resistance, with an attractive game leather appearance. The products should be washable in an ordinary home washing machine and should exhibit substantially unchanged the aforementioned properties even after at least fifty washings at a temperature of 50.degree. C. In addition, they should be resistant to all solvents used in dry cleaning such as gasoline, perchloroethylene and fluoridized solvents.